This invention is concerned with improvements relating to the melting of glass, particularly by a method involving the use of a furnace comprising a melting chamber wherein glass is continuously melted, and a working chamber from which molten glass is discontinuously withdrawn such as from time to time. The invention is particularly concerned with the melting of glass for use in the production of hand made articles, or in a hand shop molten glass being withdrawn from the working chamber as it is required for use by an artisan for the production of an article.
The term "glass" is used herein generically, and includes a variety of heat fusable vitreous materials of differing compositions.
A convenient form of glass melting furnace comprises a melting chamber containing a body of molten glass, heating means in the chamber to supply heat to the molten glass, and means to deposit solid state batch material generally onto the top of the body of molten glass such as in a cold top melter. The batch material is progressively melted from the lower surfaces of the layer, whilst molten glass flows from an outlet of the furnace chamber into a working chamber, fresh batch material being continuously supplied to the top of the melting chamber to retain the layer of batch material at a desired depth. Such a furnace is a cold top type of continuous melter with a working chamber from which molten material is intermittently withdrawn and hereinafter referred to as being of the kind specified.
Molten glass is withdrawn for use in a production process, (which may be manual or automatic) from the working chamber; if desired an intermediate chamber may be located between the melting chamber and the working chamber.
Furnaces of the kind specified are well suited to continuous, uniform production, and whilst efforts have been made to enable the output of such furnaces to be varied, it has not proved possible satisfactorily to utilise such furnaces in circumstances where the requirement for glass varies widely, particularly in a way in which the temperature of the furnace is not subjected to potentially damaging fluctuations. This is particularly the case where the heating means comprises electrodes to heat the body of molten glass by the Joule effect.
In particular, in the production of hand made articles, it has heretofor been generally necessary, when using a glass melting furnace of the kind specified, to work a full three shift system, which is in many instances unacceptable or unsatisfactory.